The present invention relates to a diamond blade for cutting and to a method of manufacturing the same, and more particularly to a diamond blade used for cutting stone, concrete, or any other workpiece, as well as to a method of manufacturing the same.
A blade used for cutting a hard material such as stone or concrete consists of a circular base plate, and a layer of super abrasive grains, such as diamond abrasive grains or CBN abrasive grains, which is bonded to the outer circumferential edge of the base plate through direct sintering, brazing, welding.
Alternatively, the blade consists of a circular base plate, and diamond segments which are fixed to the outer circumferential edge of the base plate at predetermined intervals.
When a workpiece; for example, a concrete member, is cut by use of such a diamond blade, a boundary portion (hereinafter referred to as a xe2x80x9cneckxe2x80x9d) between the diamond-abrasive-grain layer (or the diamond segment) and the base plate thinner than the diamond-abrasive-grain layer (or the diamond segment) wears considerably due to swarf which is generated during cutting and which has a strong wearing effect, with the result that the diamond-abrasive-grain layer (or the diamond segment) may drop from the base plate due to the neck wear, even if the diamond grain layer (or the diamond segment) is still usable.
In order to prevent the above-described neck wear, diamond blades as shown in FIGS. 18 and 19 have been proposed. In the diamond blade 60 shown in FIG. 18, two types of diamond segments are provided on the outer circumferential surface of a steel base plate 61. Specifically, there are provided a plurality of ordinary diamond segments 62 having an arcuate shape, and a plurality of irregular-shaped diamond segments 64 whose side surfaces extend to the vicinity of the lower end of a slot 63 formed at the outer circumference of the steel base plate 61 on the front side with respect to the rotation direction. The ratio in number between the tips 62 and 64 is set in the range of about 3:1 to 6:1 (West German Patent Application Laid-Open No. 3005324 discloses a diamond blade similar to that shown in FIG. 18).
In the diamond blade 70 shown in FIG. 19, a mixture of metal powder, and diamond or CBN abrasive grains is bonded to a steel base plate 71 through sintering. Specifically, there are provided super-abrasive-grain layers 72 and tips (each having a leg portion) 72A having a super-abrasive-grain layer which extends toward the inner circumference of the base plate in order to achieve prevention of neck wear and other effects. Therefore, the diamond blade 70 can prevent neck wear. Further, when the diamond blade 70 cuts a hard plate material or the like, the diamond blade 70 can made the cut surface smoother than can conventional diamond blades, because the leg portion of the tip extends from the center of the super-abrasive-grain layer toward the center of the base plate to thereby form a T-like shape.
The diamond blade 60 shown in FIG. 18 is effective in terms of prevention of neck wear; however, since opposite sides of the irregularly-shaped tip 64 have a large total area, cutting resistance is high, resulting in a deterioration in cutting performance. The diamond blade 70 shown in FIG. 19 has the following problem. When the diamond blade 70 cuts a workpiece, the workpiece or swarf strike the leg portions of the base plate. Further, since the leg portions hinder discharge of the swarf, the swarf stagnates between cut surfaces and the base plate. Thus, so-called neck wear is accelerated. Further, when swarf stagnates, rotational friction is generated between the cut surfaces and the base plate, so that smooth rotation of the diamond blade is hindered. Consequently, deflection occurs during rotation, resulting in deteriorated straightness of the travel path.
The present invention was accomplished to solve the above-described problems, and an object of the present invention is to provide a diamond blade which can prevent neck wear and deterioration in cutting performance simultaneously, which is inexpensive, and whose travel path has excellent straightness, as well as a method of manufacturing the diamond blade.
The present invention provides a diamond blade in which a blade portion formed of diamond abrasive grains is fixed to a base plate along the outer circumferential edge thereof, characterized in that isolated cutting elements are provided on at least a front or reverse face of the base plate such that the isolated cutting elements are separated from the blade portion fixed along the outer circumferential edge.
Since isolated cutting elements are provided on the base plate, a workpiece is cut by both the isolated cutting elements and the blade portion provided along the outer circumferential edge of the base plate, and the flow of swarf is divided into a plurality of flows, so that swarf does not concentrate at the neck, and thus neck wear can be prevented. Further, since the isolated cutting elements grind cut surfaces, the resistance generated at the side surfaces during cutting can be reduced, and the finish of cut surfaces is improved.
Preferably, the blade portion formed of diamond abrasive grains is fixed to the outer circumferential edge of the base plate by means of direct sintering, and recesses are formed alternately on the front and reverse faces of the base plate such that each recess extends from the outer circumferential edge of the base plate while inclining forward with respect to the rotation direction of the base plate. Therefore, swarf generated during cutting of a workpiece is discharged from the recesses effectively as the diamond blade rotates, whereby generation of rotational friction, which would otherwise be generated due to stagnation of swarf between cut surfaces and the base plate, can be prevented.
When, as described above, the blade portion formed of diamond abrasive grains is fixed to the outer circumferential edge of the base plate by means of direct sintering, the isolated cutting elements are preferably fixed to predetermined positions of the base plate by means of direct sintering. When formation of the blade portion of diamond abrasive grains, formation of the isolated cutting elements, and connection of these blade portions to the base plate are performed by means of direct sintering, the diamond blade can be manufactured at low cost.
Preferably, each of the isolated cutting elements has a substantially trapezoidal shape which inclines forward from the outer end thereof with respect to the rotation direction of the base plate, because this configuration maintains smooth rotation of the diamond blade. Further, the isolated cutting elements are preferably formed on a line extending from the corresponding recess.
Preferably, each section of the blade portion formed of diamond abrasive grains and located between the recesses has an extended blade portion formed on the front or reverse face of the base plate, the extended blade portion extending toward the center of the base plate and adjacent extended blade portions being spaced at predetermined intervals. Alternatively, adjacent sections of the blade portion formed of diamond abrasive grains and sandwiching the corresponding recess on the front or reverse face of the base plate are extended toward the center of the base plate, and inner ends of the extended sections are connected together to form a substantially squarish C-like. shape to thereby form at least one irregular-shaped blade portion.
When, as described above, the blade portion has an extended blade portion or irregular-shaped blade portion, a workpiece is cut by blade portions having different shapes, and the flow of swarf is divided into a plurality of flows, so that swarf does not concentrate at the neck, and thus neck wear can be prevented. Further, since the blade portions extending toward the center side grind cut surfaces, the finish of cut surfaces is improved.
Preferably, the isolated cutting elements, the extended blade portions, or the irregular-shaped blade portions are formed on both the front and the reverse faces of the base plate. In this case, the effects of preventing neck wear and improving the finish of cut surfaces can be attained on both the front and reverse faces of the base plate.
At this time, the isolated cutting elements, the extended blade portions, or the irregular-shaped blade portions are preferably formed on the front and reverse faces of the base plate with a phase difference of a predetermined angle as measured with the rotational center of the base plate serving as a vertex. In this case, the thickness of the diamond blade can be maintained constant, and therefore, the diamond blade can be rotated smoothly. In addition, since the flow of swarf is divided into a plurality of flows, swarf neither concentrates nor stagnates at one location.
Preferably, crest portions and trough (recess) portions are alternately formed on opposite faces of the base plate, so that the base plate has a wavy surface on either face. In this case, swarf can be discharged smoothly from the trough (recess) portions, and upon rotation of the blade, an air-cooling effect occurs, so that accumulation of heat at the cutting edge and the base plate can be avoided.
The present invention further provides a diamond blade in which slots are formed in a base plate at predetermined intervals, and a diamond segment is fixed to the outer circumferential surface of the base plate to be located between the corresponding slots, characterized in that each of the slots extends from the outer circumferential edge toward the center of the base plate, while inclining forward with respect to the rotation direction of the base plate; and the diamond segment has an elongated portion extending along the outer circumferential surface of the base plate and an extension portion extending from the elongated portion along the slot located on the front side of the elongated portion with respect to the rotation direction, the elongated portion and the extension portion forming an L-like shape.
As described above, the diamond blade of the present invention has a structure such that a diamond segment is fixed to the base plate having slots, and the diamond segment has an extension portion extending from the elongated portion along the slot located on the front side of the elongated portion with respect to the rotation direction to thereby form an L-like shape. Therefore, as the amount of intrusion of the diamond blade into a workpiece increases, the extension portion extending along the slot comes into contact with the workpiece, whereby cutting work proceeds.
Accordingly, the workpiece is cut and ground by means of the extension portion, and swarf is discharged from the slots. In this manner, swarf is prevented from entering the spaces between the base plate and the diamond segments, and thus neck wear is prevented. In addition, it is possible to prevent generation of rotational friction which would otherwise be generated due to stagnation of swarf between the base plate and the diamond segments.
Preferably, the extension portion extends up to a point in the vicinity of the bottom of the corresponding slot. In this case, the extension portion comes into contact with a cut surface of a workpiece over a wider range, so that the workpiece can be cut more efficiently. Preferably, the diamond segment has a projection extending toward the center of the base plate in the vicinity of the rear end with respect to the rotation direction. This structure enables the diamond segment to be reliably fixed to the base plate.
Even in the case of the diamond blade in which a diamond segment is fixed the base plate having slots, isolated cutting elements are preferably formed on at least the front or the reverse face of the base plate. In this case, the flow of swarf is divided into a plurality of flows, so that neck wear can be prevented more effectively.
In a method of manufacturing a diamond blade according to the present invention, the diamond blade is manufactured through so-called direct sintering in which sintering of the diamond segment and bonding of the diamond segment to the base plate are performed in the same step. Therefore, production cost can be reduced greatly.